Endoscopic snares may be used for tissue resection at a treatment site within a patient. For example, tissue resection may be performed in the gastrointestinal (GI) anatomy of a patient during various procedures, such as endoscopic submucosal dissection (ESD), endoscopic mucosal resection (EMR), and polpectomies. Tissue resection may be performed “hot” (i.e., with application of radio frequency (RF) current) or “cold” (i.e., without application of RF current, or manual resection). During tissue resection, either hot or cold, a distal loop of the snare is placed around a targeted tissue and is then retracted, which applies circumferential force around the tissue. For hot snares, RF current is also applied to the tissue, which cuts the tissue.
Some electrosurgical snares that apply RF current to the targeted tissue have a distal loop that is uninsulated. As such, RF current that is supplied to the distal loop is spread out along the entire length of the exposed wire that is in contact with the tissue. In addition, the wire making up the distal loop may have a constant diameter or thickness, and so the RF current may be distributed evenly (i.e., the current density may be the same) over the portions of the distal loop in contact with the tissue since the thickness and corresponding surface area are the same. If power settings of the power source generating the RF current are too low, the current density over the portions of the distal loop in contact with the tissue may be correspondingly too low, which makes it difficult and/or time consuming to initiate cutting the targeted tissue.
In addition, when the current density is too low, rather than cut the tissue, the RF current may coagulate the tissue, which may leave a ring of coagulation, even when the targeted tissue is finally cut. The ring of coagulation may make it difficult for a pathologist or a histologist to determine margins of the lesion. Also, a portion of the ring of coagulation that is left as part of the tissue in vivo may slow down tissue regeneration to cover the exposed muscle bed, which could result in delayed perforations.
While circumferentially coagulating the targeted tissue for a prolonged period of time prior to cutting may be undesirable, immediately circumferentially cutting the tissue once the RF current is applied may also be undesirable as doing so may lead to excessive bleeding. Hence, achieving a suitable balance of cutting and coagulation circumferentially around the targeted tissue during the resection process may be desirable in order to avoid both excessive coagulation and excessive bleeding.